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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 735-741 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method is developed to detect electron paramagnetic resonance (EPR) transient signals with frequency components in the range from dc to 1 MHz and a low initial signal-to-noise ratio (e.g., 0.1 after one sweep). This method uses 200-kHz magnetic field modulation on a conventional EPR spectrometer, using a modified lock-in detector: the tuned amplifier is replaced by a broadband preamplifier with a high-pass filter and the low-pass filter of the lock-in detector is replaced by a broadband amplifier. The transients are generated incoherently from the magnetic field modulation, and subsequently averaged. The function of the (removed) low-pass filter is taken over by the averaging. An instrumental response time of less than 1 μs is obtained. This was determined by measuring the rise time of the triplet state of the photosynthetic reaction center of Rhodopseudomonas sphaeroides R-26 at 165 K. This method, direct detection, and high-frequency (1–2 MHz) modulation are discussed. The S/N ratio of the method described in this paper is similar to that of the other two methods. However, when large linewidths (〉0.5 mT) are met, it gives a superior S/N ratio as compared to high-frequency (1–2 MHz) modulation methods, due to the higher maximum modulation amplitude. When the transients of interest contain frequency components in the low-frequency noise regime (dc–50 kHz), the described method is to be preferred over direct detection because of its better S/N ratio.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1976-1978 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that the leakage current through a metal–semiconductor–metal photodetector can be reduced by placing a thin interfacial silicon dioxide layer between the Schottky metal and the silicon substrate. We measure a factor 5.2 reduction in leakage-current density to 18 μA/cm2 at 5 V, a weaker increase in dark current with bias, and a factor 3.5 improvement in photoresponsivity to 0.39 A/W. We do not observe any noticeable reduction in device speed using this interfacial oxide. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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